CuO nanoparticles decorated on hydroxyapatite/ferrite magnetic support: photocatalysis, cytotoxicity, and antimicrobial response.

Photocatalysts supported in magnetic nanocomposites for application in environmental remediation processes have been evaluated for removing contaminants due to easy recovery and low toxicity to the ecosystem. In this work, copper oxide (CuO) nanoparticles with photocatalytic properties were decorated on magnetic support constituted by hydroxyapatite (HAP) and ferrite to achieve efficiency in contaminated water remediation under visible light irradiation. First, nanomaterials were obtained by precipitation route, allowing fast and straightforward synthesis. Then, CuO nanoparticles with 6 nm diameter were efficiently decorated on magnetic support (25 nm), showing a high ability to absorb visible light irradiation (bandgap) to promote electronic transition and charge separation. Under visible irradiation, CuO promotes the H2O2 reduction in the conduction band (BC) to form hydroxyl radicals (•OH), which are responsible for rhodamine B (RhB) dye degradation (> 90% in 60 min). Magnetic hysteresis assays confirmed the magnetic properties of HAP/ferrite support, which enabled the recovery and reuse of the magnetic photocatalyst efficiently up to 3 cycles. Due to low Cu2+ leaching after the photocatalytic application stage, cytotoxicity assay for the Allium cepa seeds did not exhibit abnormal cells other than those commonly found. Furthermore, the CuO-decorated nanoparticles showed bactericidal activity against S. aureus (Gram-positive) and E. coli (Gram-negative) microorganisms, being more significant for the first one. Thus, the developed nanocomposite of CuO nanoparticles decorated on the magnetic support surface showed to be a complete system for water remediation, acting in contaminant degradation under visible light irradiation and bactericidal control with environmentally friendly characteristics.Graphical abstract CuO nanoparticles decorated on hydroxyapatite/ferrite magnetic support acting as a photocatalytic and bactericidal system.

Nb2O5 nanoparticles decorated with magnetic ferrites for wastewater photocatalytic remediation.

Nanotechnology has been studied on environmental remediation processes to foster greater photocatalysts efficiency and reuse in wastewater. This study investigated the photocatalytic efficiency and viability of niobium pentoxide (Nb2O5) nanoparticles decorated with magnetic ferrite (cobalt ferrite (CoFe2O4) or magnesium ferrite (MgFe2O4)) for atrazine photodegradation. Thus, the decorated Nb2O5 was synthesized by the polymeric precursor method, forming nanoparticles with sizes ranging from 25 to 50 nm. Nanocomposite elementary analyses showed a homogeneous distribution of elements on all particles surface. Efficient magnetic saturation was observed for pure CoFe2O4 (53 emu g-1) and MgFe2O4 (19 emu g-1) nanoparticles, promoting the magnetic removal of Nb2O5:CoFe2O4 and Nb2O5:MgFe2O4 nanocomposites. Photocatalytic assays showed 88% efficiency for atrazine photodegradation with all nanomaterials, which represented a 21% increase compared to photolysis in the 1st cycle. The magnetic nanocomposites when applied to a 5th cycle maintained the atrazine photodegradation activity. In this way, magnetic Nb2O5-based nanocomposites decorated with ferrite nanoparticles showed an efficient photocatalytic response, in addition to posterior magnetic removal from the aqueous medium. Therefore, the evaluated magnetic Nb2O5 nanocomposites may be an alternative to enhance the wastewater removal process and foster the reuse in advanced oxidative processes.

Promising Nanostructured Materials against Enveloped Virus.

The development of self-disinfectant devices is highly needed to prevent and control infections, mainly caused by virus. In the past years, coronaviruses have been a threat to humanity, causing severe epidemics of respiratory infections such as severe acute respiratory syndrome (SARS), in 2003, and Middle East respiratory syndrome (MERS) in 2012, and presently the SARS-CoV2 is causing the COVID-19 pandemic. Previous studies have demonstrated that surface contamination play a significant role in the spreading of viruses. These studies demonstrated that the production of highly reactive species by copper alloys contributes to rapid elimination of viruses. Nanostructured materials such as semiconductors TiO2, Co3O4 CuO, NiO, and TiO2, and silver nanoparticles can decrease the virus viability on the surfaces when associated with polymers and textiles, especially in conditions of light exposure. In addition, graphene oxide is rising as a promising material for inactivation of viruses due to its capacity of destroying the viral envelope and capsid. The virucidal property of these materials can be enhanced by increasing their functionalization with photosensitizers. The present mini-review brings subsidies for the development of new advanced self-disinfectant materials that can be used in the manufacture of gloves, masks, and a variety of other devices.

Development of artificial muscles based on electroactive ionomeric polymer-metal composites.

This work contextualizes the research of materials that can be applied as artificial muscles. The main motivation of this research is the importance of the development of mechatronic systems for the replacement of traditional devices of actuation and motion based on rotational electrical motors by other devices that reproduce biological muscle movements. Electroactive polymers (EAPs) are materials that respond to electric stimuli with shape and/or dimension changes, and accomplish movements that are smooth enough to mimic biological muscles. Among EAPs, the ionomeric polymer-metal composites (IPMCs) are an interesting alternative to biomimetic devices due to large displacements when submitted to low applied voltage. This article presents a brief review of IPMCs, a sample preparation procedure, and some electromechanical experimental results. We also discuss the applicability of this technology in medical devices and as artificial muscles.

Deposition of controlled thickness ultrathin SnO2:Sb films by spin-coating.

The technological interest in transparent conductive oxide films (TCOs) has motivated several works in processing techniques, in order to obtain adequate routes to application. In this way, this work describes a new route to obtain antimony-doped tin oxide (ATO) films, based in colloidal dispersions of oxide nanocrystals. The nanoparticles were obtained by a hydrolisis method, using SnCl2 and SbCl3 in ethanolic solutions. The residual halides were removed by dyalisis, obtaining a limpid and transparent colloidal suspension. By this, the method offers the advantage of producing ultrathin films without organic contaminants. This route was employed to produce films with 5, 10, 14, and 18 mol% Sb doping, with thickness ranging from 40 to 70 nm. The physical characterization of the samples showed a uniform layer deposition, resulting in good packing density and high transmittance. A preliminar electrical study confirmed the low electrical resistivity even in the ultrathin films, in such level similar of reported data. The method described is similar in some aspects to layer-by-layer (LbL) techniques, allowing fine control of thickness and interesting properties for ultrathin films, however, with low cost when compared to similar routes.